Method of transmitting and receiving control information in a wireless communication system

ABSTRACT

A method of transmitting and receiving control information for a specific service in a wireless communication system is discussed. The method of transmitting control information for a specific service in a wireless communication system which uses multiple carriers includes transmitting notification indication information to at least one user equipment, the notification indication information including information related to a channel resource region through which control information for the specific service is transmitted, and transmitting a notification message to the at least one user equipment through the channel resource region indicated by the information related to the channel resource region, the notification including control information.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.12/438,318 filed May 8, 2009, now U.S. Pat. No. 8,155,648 which is anational stage of PCT Application No. PCT/KR2007/004012 filed Aug. 22,2007, which claims priority to Korean Patent Application No.10-2007-0080363 filed Aug. 9, 2007 and to U.S. Provisional ApplicationSer. No. 60/823,247 filed Aug. 22, 2006. The contents of each of theseapplications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wireless communication system, andmore particularly, to a method of transmitting and receiving controlinformation for a specific service in a wireless communication system.

2. Discussion of the Background Art

A multimedia broadcast/multicast service (hereinafter, referred to as“MBMS”) is to provide a streaming or background service to a pluralityof user equipments by using a downlink dedicated MBMS bearer service. Ina network, an MBMS bearer uses a point-to-multipoint wireless bearerservice or a point-to-point wireless bearer service.

The MBMS is divided into a broadcast mode and a multicast mode. The MBMSbroadcast mode is a service for transmitting multimedia data to all userequipments (UEs) within a broadcast area. The broadcast area refers to aregion where the broadcast service is possible. On the other hand, theMBMS multicast mode is a service for transmitting the multimedia data toa specific user equipment group only within a multicast area. Themulticast area refers to a region where the multicast service ispossible.

A procedure of providing a specific MBMS from a network to a userequipment by using a multicast mode will be described below. First ofall, user equipments which desire to receive the MBMS should undergo asubscription procedure. Subscription refers to establishing arelationship between a service provider and a user equipment. Also, theuser equipments which desire to receive the MBMS should receive aservice announcement provided by the network. The service announcementrefers to providing the user equipments with a list of services to beprovided and related information of the services.

Meanwhile, a user equipment which desires to receive the MBMS of themulticast mode should join a multicast group specifically. The multicastgroup refers to a group of user equipments which receive a specificmulticast service, and joining refers to merging with a multicast groupto receive the specific multicast service. The user equipment can notifythe network through the above joining that it desires to receivespecific multicast data. On the other hand, the user equipment which hasjoined the multicast group can unsubscribe to joining of the multicastgroup, which is referred to as leaving.

Each user equipment performs the subscription, joining and leavingprocedures. The user equipment can perform the subscription, joining,and leaving procedures at any time, such as before data transmission,during the data transmission, or after the data transmission.

The MBMS can be divided into a multi-cell service and a single cellservice, wherein the multi-cell service is to provide a service to aplurality of cells, and the single cell service is to provide a serviceto a single cell. The multi-cell service provides the service through amulticast channel (MCH), and the single cell service provides theservice through a downlink shared channel (DL SCH). If the userequipment receives the multi-cell service through the MCH, the userequipment can receive the same multi-cell service transmitted fromvarious cells by combining in an MBMS single frequency network (MBSFN)mode.

To provide the MBMS, the network provides MBMS control channel (MCCH)and MBMS traffic channel (MTCH). The MCCH is used to transmit controlinformation for MBMS transmission to the user equipment while the MTCHis used to transmit the MBMS to the user equipment. The MBMS iscomprised of one or more sessions, wherein only one session can existduring one time interval.

SUMMARY OF THE INVENTION

The network can conventionally transmit MBMS notification messagethrough the MCCH to notify user equipments of a start of session of theMBMS or change of MBMS control information. The MCCH is transmittedthrough a semi-static radio resource. However, a problem occurs in thiscase. That is, since the MCCH is transmitted through such a semi-staticradio resource, if there is any change in either a size of MCCHinformation or a radio channel, it is difficult to promptly respond tothe change, whereby the radio resource is used inefficiently.

Accordingly, the present invention is directed to a method oftransmitting and receiving control information in a wirelesscommunication system, which substantially obviates one or more problemsdue to limitations and disadvantages of the related art.

An object of the present invention is to provide a method oftransmitting and receiving control information in a wirelesscommunication system to efficiently use radio resources.

Another object of the present invention is to provide a method oftransmitting and receiving control information in a wirelesscommunication system, in which certainty in receiving controlinformation for a specific service is assured.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, anetwork includes a notification indicator channel and a control channelto notify change of control information of a specific service, therebyefficiently using a radio resource. An identifier corresponding to theservice and transport information of the control channel to which thecontrol information is transmitted are transmitted through thenotification indicator channel.

In another aspect of the present invention, a user equipment whichreceives the specific service from the network receives the notificationindicator channel, and receives the control channel using the transportinformation if the above identifier corresponds to an identifier storedin the user equipment.

Preferably, the identifier is a service identifier or service groupidentifier for identifying the service, or a session identifier orsession group identifier for identifying a session of the service. Theuser equipment does not receive the control channel if the aboveidentifier does not correspond to an identifier stored in the userequipment.

Preferably, the notification indicator channel is an L1/L2 controlchannel or a physical downlink control channel (PDCCH).

Preferably, the transport information is information included in thecontrol channel which transmits the control information or thenotification message which notifies the control information, andincludes establishment of modulation/coding for transmission of thecontrol channel corresponding to a transport time of the notificationindicator channel, resource block, time frame, HARQ information, etc.

Preferably, the user equipment which has received the notificationindicator channel receives the notification message through the controlchannel if the identifier is included in the notification indicatorchannel. If a specific transport time of the control information isdesignated in the notification message, the user equipment receives thecontrol channel in the designated specific time.

In still another aspect of the present invention, a method oftransmitting control information for a specific service in a wirelesscommunication system which uses multiple carriers comprises transmittingnotification indication information to at least one user equipment, thenotification indication information including information related to achannel resource region through which control information for thespecific service is transmitted, and transmitting a notification messageto the at least one user equipment through the channel resource regionindicated by the information related to the channel resource region, thenotification including control information.

In further still another aspect of the present invention, a method ofreceiving control information for a specific service in a wirelesscommunication system which uses multiple carriers comprises receivingnotification indication information from a network, the notificationindication information including information related to a channelresource region through which control information for the specificservice is transmitted, and receiving a notification message from thenetwork by using the notification indication information, thenotification including control information.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a network structure of an E-UMTS (Evolved-UniversalMobile Telecommunications System);

FIG. 2 is a schematic view illustrating an E-UTRAN (UMTS terrestrialradio access network);

FIG. 3A and FIG. 3B illustrate a structure of a radio interface protocolbetween a user equipment (UE) and E-UTRAN, in which FIG. 3A is aschematic view of a control plane protocol and FIG. 3B is a schematicview of a user plane protocol;

FIG. 4 illustrates an example of a structure of physical channels usedin an E-UMTS system; and

FIG. 5 illustrates a frame structure in an E-UMTS system according tothe embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, structures, operations, and other features of the presentinvention will be understood readily by the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Embodiments described later are examples in which technicalfeatures of the present invention are applied to E-UMTS (EvolvedUniversal Mobile Telecommunications System).

FIG. 1 illustrates a network structure of an E-UMTS. An E-UMTS is asystem evolving from the conventional WCDMA UMTS and its basicstandardization is currently handled by the 3GPP (3^(rd) GenerationPartnership Project). The E-UMTS can also be called an LTE (Long TermEvolution) system. Release 7 and Release 8 of 3GPP technicalspecifications (3^(rd) Generation Partnership Project; TechnicalSpecification Group Radio Access Network) can be referred to obtaindetailed information about the UMTS and E-UMTS.

Referring to FIG. 1, an E-UTRAN includes base stations (hereinafter,referred to as ‘eNode B’ or ‘eNB’), wherein respective eNBs areconnected with each other through X2 interface. Also, each of eNBs isconnected with a user equipment (UE) through a radio interface andconnected with EPC (Evolved Packet Core) through S1 interface. The EPCcomprises MME (Mobility Management Entity) and a SAE (SystemArchitecture Evolution) gateway.

Layers of a radio interface protocol between a UE and a network can beclassified into a first layer L1, a second layer L2 and a third layer L3based on three lower layers of OSI (open system interconnection)standard model widely known in communication systems. A physical layerbelonging to the first layer L1 provides an information transfer serviceusing a physical channel. A radio resource control (hereinafter,abbreviated as ‘RRC’) located at the third layer plays a role incontrolling radio resources between the UE and the network. For this,the RRC layer enables RRC messages to be exchanged between the UE andthe network. The RRC layer can be distributively located at networknodes including Node B, an AG and the like or at either the Node B orthe AG.

FIG. 2 is a schematic view illustrating an E-UTRAN (UMTS terrestrialradio access network). In FIG. 2, a hatching part represents functionalentities of a user plane and a non-hatching part represents functionalentities of a control plane.

FIG. 3A and FIG. 3B illustrate a structure of a radio interface protocolbetween the user equipment (UE) and the E-UTRAN, in which FIG. 3A is aschematic view of a control plane protocol and FIG. 3B is a schematicview of a user plane protocol. Referring to FIG. 3A and FIG. 3B, a radiointerface protocol vertically includes a physical layer, a data linklayer, and a network layer and horizontally includes a user plane fordata information transfer and a control plane for signaling transfer.The protocol layers in FIG. 3A and FIG. 3B can be classified into L1(first layer), L2 (second layer), and L3 (third layer) based on threelower layers of the open system interconnection (OSI) standard modelwidely known in the communications systems.

The physical layer as the first layer provides information transferservice to an upper layer using physical channels. The physical layer(PHY) is connected to a medium access control (hereinafter, abbreviatedas ‘MAC’) layer above the physical layer via transport channels. Dataare transferred between the medium access control layer and the physicallayer via the transport channels. Moreover, data are transferred betweendifferent physical layers, and more particularly, between one physicallayer of a transmitting side and the other physical layer of a receivingside via the physical channels. The physical channel of the E-UMTS ismodulated according to an orthogonal frequency division multiplexing(OFDM) scheme, and time and frequency are used as radio resources.

The medium access control (hereinafter, abbreviated as ‘MAC’) layer ofthe second layer provides a service to a radio link control(hereinafter, abbreviated as ‘RLC’) layer above the MAC layer vialogical channels. The RLC layer of the second layer supports reliabledata transfer. In order to effectively transmit IP packets (e.g., IPv4or IPv6) within a radio-communication period having a narrow bandwidth,a PDCP layer of the second layer (L2) performs header compression toreduce the size of a relatively-large IP packet header containingunnecessary control information.

A radio resource control (hereinafter, abbreviated as ‘RRC’) layerlocated on a lowest part of the third layer is defined in the controlplane only and is associated with configuration, reconfiguration andrelease of radio bearers (hereinafter, abbreviated as ‘RBs’) to be incharge of controlling the logical, transport and physical channels. Inthis case, the RB means a service provided by the second layer for thedata transfer between the UE and the UTRAN.

As downlink transport channels carrying data from the network to UEs,there are provided a broadcast channel (BCH) carrying systeminformation, a paging channel (PCH) carrying paging message, and adownlink shared channel (SCH) carrying user traffic or control messages.The traffic or control messages of a downlink multicast or broadcastservice can be transmitted via the downlink SCH or an additionaldownlink multicast channel (MCH). Meanwhile, as uplink transportchannels carrying data from UEs to the network, there are provided arandom access channel (RACH) carrying an initial control message and anuplink shared channel (UL-SCH) carrying user traffic or control message.

As logical channels located above the transport channels and mapped withthe transport channels, there are provided a broadcast channel (BCCH), apaging control channel (PCCH), a common control channel (CCCH), amulticast control channel (MCCH), and a multicast traffic channel(MTCH).

In the E-UMTS system, an OFDM is used on the downlink and a singlecarrier frequency division multiple access (SC-FDMA) on the uplink. TheOFDM scheme using multiple carriers allocates resources by unit ofmultiple sub-carriers including a group of carriers and utilizes anorthogonal frequency division multiple access (OFDMA) as an accessscheme.

A physical layer of an OFDM or OFDMA scheme divides active carriers intoa plurality of groups and transmits respective groups to differentreceiving sides. Radio resource allocated to each UE which is defined bya time-frequency region on a two-dimensional sphere comprises continuoussub-carriers. A time-frequency region in the OFDM or OFDMA scheme is arectangular form sectioned by time and sub-carrier coordinates. In otherwords, one time-frequency region could be a rectangular form sectionedby at least one symbol on a time axis and sub-carriers on a frequencyaxis. Such a time-frequency region can be allocated to an uplink for aspecific UE, or an eNB can transmit the time-frequency region to aspecific UE in a downlink. In order to define such a time-frequencyregion on the two-dimensional sphere, the number of OFDM symbols and thenumber of continuous sub-carriers starting from a point having an offsetfrom a reference point should be given.

The E-UMTS which is currently being discussed uses 10 ms radio framecomprising 20 sub-frames. Namely, a sub-frame has a length of 0.5 ms. Aresource block comprises one sub-frame and twelve sub-carriers, each ofwhich is 15 kHz. One sub-frame comprises a plurality of OFDM symbols anda part (for example, first symbol) of the plurality of OFDM symbols canbe used for transmission of L1/L2 control information.

FIG. 4 is a diagram illustrating a structure of physical channels usedin the E-UMTS. In FIG. 4, a sub-frame comprises an L1/L2 controlinformation transmission region (the hatching part) and a datatransmission region (the non-hatching part).

FIG. 5 illustrates a frame structure in the E-UMTS system according tothe embodiment of the present invention. In FIG. 5, E-UMTS networkprovides a specific MBMS service to at least one user equipment.

Referring to FIG. 5, the E-UMTS network transmits an MBMS notificationmessage to a user equipment if control information for the specific MBMSservice is changed or a session of the specific MBMS service starts orstops. Also, the E-UMTS network transmits MBMS notification indicationinformation to the user equipment to previously notify that the MBMSnotification message is transmitted. As shown in FIG. 5, the MBMSnotification indication information can be transmitted through a L1/L2control information region, and the MBMS notification message can betransmitted through a data region.

The MBMS notification message may include identification information(identifier) of the MBMS, control information which has been changed,and information about start and stop of a session or start of counting.The MBMS notification indication information may include an MBMSidentifier or an MBMS group identifier and indication information ofchannel resource region (for example, a position of resource blocksallocated to the MBMS notification message on a frame), through whichthe MBMS notification message is transmitted. The resource blockallocated to the MBMS notification message is a two-dimensional regionon a time-frequency plane and can be expressed by a sub-carrier offset,the number of sub-carriers, a symbol offset, and the number of symbols.

As described above, in the OFDM or OFDMA system, the radio resourceallocated to each UE is defined by a two-dimensional time-frequencyregion, and is a set of continuous sub-carriers. In the OFDM or OFDMAsystem, one time-frequency region is a rectangular form determined bytime and sub-carrier coordinates. In other words, one resource blockcould be a rectangular form sectioned by at least one symbol on a timeaxis and a plurality of sub-carriers on a frequency axis.

The MBMS notification indication information may further includetransport format indication information (for example, a coding scheme, amodulation scheme, or HARQ information, etc.) of the MBMS notificationmessage. The MBMS notification indication information may also notify asize of a protocol data unit (PDU) which includes the MBMS notificationmessage. The MBMS notification message is transmitted through the MCCHwhich is a logical channel, wherein the MCCH channel can be transmittedon MCH or DL SCH which is a transport channel. The number of resourceblocks allocated to the MBMS notification message is determined by thesize of the MBMS notification message.

The user equipment which has received the MBMS stores an identifiercorresponding to the received service. The user equipment periodicallyreceives the L1/L2 control channel which transmits the MBMS notificationindication information or non-periodically receives the same channel ifa predetermined event occurs. The user equipment of an idle modereceives the L1/L2 control channel periodically, i.e., at a receivingperiod of a paging message. The user equipment of an RRC connection modereceives the L1/L2 control channel periodically, i.e., at a DRX periodor MBMS dedicated period, wherein the service can be broadcasted throughsystem information.

The user equipment receives the MBMS notification indication informationthrough the L1/L2 control channel. If the MBMS identifier included inthe received MBMS notification indication information is the same as orcorresponds to the MBMS identifier stored in the user equipment, theuser equipment receives the MCH or the DL SCH using information includedin the MBMS notification indication information, wherein the MBMSnotification message is transmitted on the MCH or the DL SCH. In otherwords, the user equipment receives the MCH or the DL SCH, through whichthe MBMS notification message is transmitted, using channel resourceregion indication information (for example, time frame, resource block,etc.), transport format indication information (for example, a codingscheme, a modulation scheme, HARQ information, etc.) and a PDU size,which are included in the MBMS notification indication information.

If the MBMS notification message is transmitted through the MCH, theuser equipment can identify an allocated channel resource region andtransport format information through system information or the MCCH,wherein the MCH is transmitted through the designated channel resourceregion. At this time, if the MBMS identifier included in the L1/L2control channel is the same as or corresponds to the MBMS identifierstored in the user equipment, the user equipment receives the MCH usingtransport format information through the designated channel resourceregion.

The MBMS notification indication information can notify as to whether atransport channel, which is to be received to acquire controlinformation or MBMS notification message for the MBMS, is MCH or DL SCH.The user equipment can receive the MBMS notification message or controlinformation by receiving the MCH or DL SCH in accordance with the MBMSnotification indication information.

Furthermore, the E-UMTS network can notify as to whether the transportchannel, which is to be received to acquire control information for theMBMS through the MBMS notification message, is the MCH or the DL SCH.For example, the user equipment receives the MBMS notification messagethrough the DL SCH in accordance with the MBMS notification indicationinformation. If the MBMS notification message notifies a specific MCHfor the MBMS, the user equipment receives the control informationthrough the corresponding MCH. If the MBMS notification message notifiesa specific DL SCH for the MBMS, the user equipment receives the controlinformation through the corresponding DL SCH.

According to the present invention, the wireless communication systemcan efficiently use the radio resource, and the user equipment canassure certainty in receiving control information for a specificservice.

It will be apparent to those skilled in the art that the presentinvention can be embodied in other specific forms without departing fromthe spirit and essential characteristics of the invention. Thus, theabove embodiments are to be considered in all respects as illustrativeand not restrictive. The scope of the invention should be determined byreasonable interpretation of the appended claims and all change whichcomes within the equivalent scope of the invention are included in thescope of the invention.

Industrial Applicability

The present invention can be applied to a wireless communication systemsuch as a mobile communication system or a wireless internet system.

The invention claimed is:
 1. A method of transmitting controlinformation for a multimedia broadcast/multicast service (MBMS) in anorthogonal frequency division multiplexing (OFDM) wireless communicationsystem, the method comprising: transmitting indication informationincluding an MBMS related identifier to at least one user equipmentthrough one or more first OFDM symbols in a subframe; and transmittingcontrol information which has been changed, via a multicast controlchannel (MCCH) to the at least one user equipment after the transmissionof the indication information, wherein the indication informationfurther includes information about which channel is related to thecontrol information, and wherein the indication information istransmitted through an L1/L2 control channel.
 2. The method of claim 1,wherein the MBMS related identifier is an MBMS identifier or an MBMSgroup identifier.
 3. The method of claim 1, wherein the controlinformation is transmitted through a data region.
 4. The method of claim1, wherein the indication information further includes channel resourceinformation through which the control information is transmitted.
 5. Themethod of claim 4, wherein the indication information further includes atransport format indication of the control information.
 6. The method ofclaim 1, wherein the control information is transmitted to the at leastone user equipment through resources designated by system information.7. The method of claim 1, wherein the indication information isperiodically transmitted to the at least one user equipment.
 8. A methodof receiving control information for a multimedia broadcast/multicastservice (MBMS) in an orthogonal frequency division multiplexing (OFDM)wireless communication system, the method comprising: receivingindication information including an MBMS related identifier from anetwork through one or more first OFDM symbols in a subframe; andreceiving control information which has been changed, via a multicastcontrol channel (MCCH), from the network based on the indicationinformation, wherein the indication information further includesinformation about which channel is related to the control information,and wherein the indication information is transmitted through an L1/L2control channel.
 9. The method of claim 8, wherein the MBMS relatedidentifier is an MBMS identifier or an MBMS group identifier.
 10. Themethod of claim 8, wherein the control information is received through adata region.
 11. The method of claim 8, wherein the indicationinformation further includes channel resource information through whichthe control information is transmitted.
 12. The method of claim 11,wherein the indication information further includes a transport formatindication of the control information.
 13. The method of claim 8,wherein the control information is received from the network throughresources designated by system information.
 14. The method of claim 8,wherein the indication information is periodically transmitted from thenetwork.